I have just received from Amazon the Netgear RND2000 Diskless NAS (cough..won on SU contest).
I don't have Sata Hard disks at home so I just turned it ON to check the boot.
After a loud noise at start, fan goes down but stays louder than a standard pc.
From your experience, is that because it is not running in normal mode (without HD) or is it really that noisy?

Edit:

I've mounted the Sata Harddisk and I've got to say that this NAS is pretty quiet.

Found this comment: The ReadyNAS is very quiet. When it first was formatting the drives the fan ran at full speed and was noisy but then they slowed down to 1500 RPM and you hardly can hear it
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systempuntooutSep 13 '10 at 21:14

I don't have one of these, but a lot of those enclosures have really small fans. If you buy a larger, higher quality fan, you won't hear it nearly as much. Usually a little work with a Dremel does the trick.

Also, depending on your drives you might not need the fan at all. This isn't likely though... drives seem to run hotter and hotter these days.

It's incredibly noisy - much noisier than my desktop PC. Even when the drives are in standby mode it's still noisy, which I really don't understand. I have it in my bedroom so I can't sleep with it on, and it's very annoying as it takes a few minutes to boot whenever I want to use it. I'm going to have to get rid of it unfortunately.